Incredibly bad-or defective item?

I appreciate DEVOLO normally.

I have two CPL of this brand, the 500 + av. They work wonderfully. I wanted to increase the speed of my connection (since my ISP has dramatically increased its speed also) by purchasing these new CPL 1200.

Horror tested, where my 500 + av reached without any difficulty speeds between 120 and 200 mbps (halving since it is transmitting and receiving), these new 1200 painfully reach speeds of 60 mbps, usually, I get stuck at 20 mbps is 6 to 10 times worse than on my old adapters of the same brand (taken on the same identical config) !!!!

Believing that it was with a problem, I tried all combinations without success.

Only one thing works less correctly: the combination of an old 500 + av (in transmission) and a 1200 (in reception). But I did not pay 140 euros for results identical to those I had before.

I then tried to update the software microphone. Once done, I get no different or better result.

Also, my computer speakers (Focal XS) when I run a speedtest with these adapters produce spitting as if the voltage varied significantly over the outlet.

I am very unhappy with these new DEVOLO and I hope it is only a defective product. I'll try a replacement and I will update my review.